Use the finger test or a moisture meter to check the soil. Pull back the mulch and stick your fingers an inch or two into the soil – if they come up clean, it's time to water.
Test by squeezing a handful of soil together. Open your hand out giving it a small shake as you do. If the soil mostly holds together and a few crumbs fall away then it's perfectly moist. If it holds its shape and you can infact shape it into something – way too wet.
Place approximately one tablespoon of soil in palm. Add water a drop at a time and knead the soil to break down all aggregates. Soil is at the proper consistency when plastic and mobile, like moist putty. Sand particle size should be estimated (very fine, fine, medium, coarse) for these textures.
Add baking soda to one jar and mix. Then add vinegar to the other and mix. If the baking soda mixture bubbles, you likely have acidic soil; if the vinegar mixture bubbles, you likely have alkaline soil. This method is best used as an initial assessment of your soil pH or as an educational activity.
Use the finger test or a moisture meter to check the soil. Pull back the mulch and stick your fingers an inch or two into the soil – if they come up clean, it's time to water. Use a moisture meter and follow the gauge if you don't want to get your hands dirty.
How to Keep Soil Moist by Adding Compost. Compost can hold several times more moisture than dry soil particles. Adding compost to your soil allows the soil to hold onto more moisture, keeps precious microbiology alive (which helps plants thrive), and feeds your plant low amounts of plant food.
Soil moisture sensors measure or estimate the amount of water in the soil. These sensors can be stationary or portables such as handheld probes. Stationary sensors are placed at the predetermined locations and depths in the field, whereas portable soil moisture probes can measure soil moisture at several locations.
Can you touch soil with bare hands? Of course you can. People have been doing this since the beginning of time. But, if you have cuts or open wounds, then bacteria, fungi, and other creatures and contaminates could enter so it's wise to wear gloves when handling soil to protect from infection.
Add half a cup of water, and mix. Then, add 1/2 cup of baking soda. If the soil bubbles or fizzes, the soil is highly acidic. The reaction you're seeing is the result of acidic soil coming into contact with an alkaline substance (baking soda).
The Finger Dip Test:
Push your finger into the soil up to your second knuckle. If the soil is moist it will stick to your finger and your plant is okay on the water front. If the soil is dry your finger will come out clean and it is time to water your indoor plants.
Touch and feel: Take a handful of soil and squeeze it gently. Dry soil will feel loose, sandy, and will not hold its shape. Moist soil, on the other hand, will clump together and hold its form when squeezed. However, be careful not to confuse excessively wet soil with overly dry soil.
Tensiometers are devices that measure soil moisture tension. They are sealed, water-filled tubes with a porous ceramic tip at the bottom and a vacuum gauge at the top. They are inserted in the soil to plants' root zone depth.
Soil water monitoring
Many types of soil moisture sensors are available for farmers to purchase. All have their strengths and weaknesses. Generally, the more sensors that you can afford to place in a field, the more likely you are to get an accurate estimate of the moisture status of the crop.
Finger Test
If the soil clings to your fingers and feels moist to touch, don't water. If, soil falls loosely off your fingers and is dry to the touch, then water.
Vermiculite, a natural mineral, has exceptional water-holding capacity and helps to improve soil moisture levels. Perlite, another commonly used inorganic additive, improves water drainage and aeration in the soil, preventing waterlogging and promoting healthy root development.
Mulch helps retain soil moisture, decreases weeds, reduces erosion, helps cool plant roots, adds organic matter (provided organic mulch is used), increases the attractiveness of the landscape, and protects plants from adverse winter conditions.
To perform the thumb penetration test, simply press the end of your thumb into a fresh clump of soil. If the soil sample is Type A, your thumb will only make an indentation in the soil with great effort, as you can see demonstrated here.
Check for soil moisture.
If the soil feels dry three or four inches below the surface, water. A common rule of thumb is that most plants need the equivalent of one inch of rainfall a week, on average—enough to soak into the soil about six inches. However, in hot weather, plants may need more.
The volumetric moisture content can also be estimated from the moisture content estimated on dry weight basis. The most common instrument used for estimating soil moisture by indirect methods is; tensiometer, gypsum block, neutron probe, pressure plate and pressure membrane apparatus.
The Screwdriver Test for Soil Moisture
Take a screwdriver (or soil probe or shovel), stick it 3–4 inches into the ground, and wiggle it around. Then reach into the hole and feel for any moisture. If your hand comes up dry, you should water your lawn.
Poke your finger into the soil
You can reach 2-3in into the soil and feel how moist or dry the soil is. This technique works best for smaller potted plants because of limited reach. Be careful not to damage roots when you try this technique; if you feel roots try another area in the pot.